Comparison of Phytophthora sojae populations in Iowa and Nebraska to identify effective Rps genes for Phytophthora stem and root rot management

2021 ◽  
Author(s):  
Rashelle Matthiesen-Anderson ◽  
Clarice Schmidt ◽  
Vinicius C. Garnica ◽  
Loren Giesler ◽  
Alison E Robertson
Keyword(s):  
Root Rot ◽  
Partial Resistance ◽  
Specific Resistance ◽  
Phytophthora Sojae ◽  
Soybean Variety ◽  
Soybean Cultivars ◽  
Soybean Genotypes ◽  
Rps Gene ◽  
High Level ◽  
Almost All

Phytophthora stem and root rot (PSRR) of soybean, caused by the oomycete Phytophthora sojae, is prevalent in Iowa and Nebraska. Reducing losses to PSRR primarily relies on growing cultivars with specific resistance (Rps) genes. Predominant genes used in commercial soybean cultivars include Rps 1a, Rps 1c, Rps 1k, and Rps 3a. Knowing which Rps gene to deploy depends on knowledge of which genes are effective against the pathogen. From 2016 to 2018, 326 isolates of P. sojae from were recovered from fields in Iowa and Nebraska and classified into pathotypes based on their virulence on 15 soybean genotypes. A total of 15 and 10 pathotypes were identified in Iowa and Nebraska, respectively. Almost all isolates were virulent on Rps 1a, while over 70% of isolates were virulent on Rps 1c and Rps 1k. Only 2.3% of isolates from Iowa were virulent on Rps 3a. Among commercial soybean cultivars tested in the Illinois Soybean Variety trials from 2010 to 2020, Rps 1c was always the most frequently reported gene followed by Rps 1k. In contrast, Rps 1a and Rps 3a were present in less than 10% and less than 5 % of the cultivars tested, respectively. Since many of the P. sojae isolates in our study were virulent on Rps 1a, Rps 1c, and Rps 1k, soybean cultivars with these genes are unlikely to provide protection against PSRR unless they have a high level of partial resistance.

scholarly journals Effect of Partial Resistance on Phytophthora Stem Rot Incidence and Yield of Soybean in Ohio

Plant Disease ◽  
2003 ◽  
Vol 87 (3) ◽  
pp. 308-312 ◽  
Author(s):  
A. E. Dorrance ◽  
S. A. McClure ◽  
S. K. St. Martin
Keyword(s):  
Partial Resistance ◽  
Phytophthora Sojae ◽  
Stem Rot ◽  
Environment Interaction ◽  
Genetic Traits ◽  
Soybean Cultivars ◽  
Negative Effect ◽  
Effect On Yield ◽  
Rps Gene ◽  
Disease Pressure

Phytophthora root and stem rot of soybean commonly causes losses in both stand and yield in Ohio. Environmental conditions which favor the pathogen typically occur in many areas of the state during late spring and summer. This study examined the performance of 12 soybean cultivars with partial resistance, with or without Rps genes, to different populations of Phytophthora sojae and various levels of disease pressure. The soybean cultivars were evaluated in seven field environments with and without metalaxyl over 4 years. There was a highly significant genotype-environment interaction which was due in part to variable disease pressure. The incidence of Phytophthora stem rot in subplots ranged from 0 to 10 plants in the most susceptible cultivar, Sloan, while significantly less stem rot developed in cultivars with high levels of partial resistance or partial resistance combined with an Rps gene in three of the seven environments. Metalaxyl applied in-furrow had a significant effect on early and final plant populations as well as yield (P < 0.001) in two of the seven environments, and for yield (P = 0.05) in one environment. This indicates that at these two environments, 2001 Lakeview and VanBuren, early season Phytophthora disease was controlled with the in-furrow fungicide treatment. When diverse populations of P. sojae were present, yields from soybean cultivars with high levels of partial resistance were significantly higher than those with low levels of partial resistance. Soybean cultivars with specific resistance genes Rps1k, Rps1k + Rps6, or Rps1k +Rps3a had higher yields than plants with only partial resistance in environments where race determination indicated that the populations of P. sojae present were not capable of causing disease on plants with the Rps1k gene. However, in an environment with very low disease pressure, yields of soybean cultivars with partial resistance were not significantly different from those with single Rps genes or Rps gene combinations. These results demonstrate that genetic traits associated with high levels of partial resistance do not have a negative effect on yield. Soybean cultivars that had the most consistent ranking across environments were those with moderate levels of partial resistance in combination with either Rps1k or Rps3a.

scholarly journals Population Structure Among and Within Iowa, Missouri, Ohio, and South Dakota Populations of Phytophthora sojae

Plant Disease ◽  
2016 ◽  
Vol 100 (2) ◽  
pp. 367-379 ◽  
Author(s):  
S. Stewart ◽  
A. E. Robertson ◽  
D. Wickramasinghe ◽  
M. A. Draper ◽  
A. Michel ◽  
...  
Keyword(s):  
Gene Flow ◽  
South Dakota ◽  
Genotypic Diversity ◽  
Phytophthora Sojae ◽  
Field Variation ◽  
Limited Gene Flow ◽  
Rps Gene ◽  
Pathogen Populations ◽  
High Level ◽  
Important Disease

Phytophthora root and stem rot, caused by Phytophthora sojae, is an economically important disease of soybean throughout the Midwestern United States. This disease has been successfully managed with resistance (Rps) genes; however, pathogen populations throughout the Midwest have developed virulence to many Rps genes, including those that have not been deployed. To gain a better understanding of the processes that influence P. sojae evolution, the population genetic structure was compared among populations using one isolate collected from 17, 33, and 20 fields in Iowa, Ohio, and South Dakota, respectively, as well as multiple isolates from individual fields in Iowa, Ohio, and Missouri. Genotypic diversity was measured using 21 polymorphic microsatellite (simple-sequence repeat) markers. and pathotype diversity using 15 soybean differentials. For all but three of the populations with low sample size, there was a high level of pathotype diversity and a low to moderate level of genotypic diversity among the populations for both comparisons between states and within-field variation. None of the Rps-gene differentials were resistant to all of the isolates. There were 103 unique multilocus genotypes identified in this study and only 2 were identified from the same field. Although no clones were identified in more than one field, pairwise FST indicated that some gene flow within neighboring fields does occur but not across the region, including fields from neighboring states. These results suggest that there is a strong probability that each state may have their own or several regional populations, as well as provide further evidence of high diversity within this homothallic pathogen which may be due, in part, to limited gene flow, mutation, or outcrossing, and this likely affects the success of deployment of resistance.

scholarly journals Races of Phytophthora sojae and Their Virulences on Soybean Cultivars in Heilongjiang, China

Plant Disease ◽  
2010 ◽  
Vol 94 (1) ◽  
pp. 87-91 ◽  
Author(s):  
Shuzhen Zhang ◽  
Pengfei Xu ◽  
Junjiang Wu ◽  
Allen G. Xue ◽  
Jinxiu Zhang ◽  
...  
Keyword(s):  
Phytophthora Sojae ◽  
Heilongjiang Province ◽  
Plant Mortality ◽  
Pathogen Population ◽  
Sources Of Resistance ◽  
Breeding Programs ◽  
Soybean Cultivars ◽  
Rps Gene ◽  
First Time ◽  
Important Disease

Phytophthora root and stem rot, caused by Phytophthora sojae, is an economically important disease of soybean (Glycine max) in Heilongjiang Province, China. The objectives of this research were to determine the race profile of P. sojae in Heilongjiang and evaluate soybean cultivars for reactions to the pathogen races. A total of 96 single-zoospore P. sojae isolates were obtained from soil samples collected from 35 soybean fields in 18 counties in Heilongjiang from 2005 to 2007. Eight races of P. sojae, including races 1, 3, 4, 5, 9, 13, 44, and 54, were identified on a set of eight differentials, each containing a single resistance Rps gene, from 80 of the 96 isolates. Races 1 and 3 were predominant races, comprising 58 and 14 isolates, and representing 60 and 7% of the pathogen population, respectively. Races 4, 5, 44, and 54 were identified for the first time in Heilongjiang, and each was represented by two to three isolates only. Sixty-two soybean cultivars commonly grown in Heilongjiang Province were evaluated for their resistance to the eight P. sojae races identified using the hypocotyl inoculation technique. Based on the percentage of plant mortality rated 5 days after inoculation, 44 cultivars were resistant (<30% mortality) to at least one race. These cultivars may be used as sources of resistance in soybean breeding programs.

Pathotype Complexity and Genetic Characterization of Phytophthora sojae Populations in Illinois, Indiana, Kentucky, and Ohio

2021 ◽  
Author(s):  
Linda Weber Hebb ◽  
Carl A. Bradley ◽  
Santiago Xavier Mideros ◽  
Darcy E. P. Telenko ◽  
Kiersten Wise ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Resistance Genes ◽  
Genetic Characterization ◽  
Specific Resistance ◽  
Agricultural Practices ◽  
Phytophthora Sojae ◽  
Simple Sequence Repeat Markers ◽  
Rps Gene ◽  
Simple Sequence

Phytophthora sojae, the causal agent of Phytophthora root and stem rot of soybean, has been managed with single Rps genes since the 1960’s, but has subsequently adapted to many of these resistance genes, rendering them ineffective. The objective of this study was to examine the pathotype and genetic diversity of P. sojae from soil samples across Illinois, Indiana, Kentucky, and Ohio by assessing which Rps gene(s) were still effective and identifying possible population clusters. There were 218 pathotypes identified from 473 P. sojae isolates with an average of 6.7 out of 15 differential soybean lines exhibiting a susceptible response for each isolate. Genetic characterization of 103 P. sojae isolates from across Illinois, Indiana, Kentucky, and Ohio with 19 simple sequence repeat markers identified 92 multilocus genotypes. There was a moderate level of population differentiation among these four states, with pairwise FST values ranging from 0.026 to 0.246. There was also moderate to high levels of differentiation between fields, with pairwise FST values ranging from 0.071 to 0.537. Additionally, cluster analysis detected the presence of P. sojae population structure across neighboring states. The level of pathotype and genetic diversity, in addition to the identification of population clusters, supports the hypothesis of occasional outcrossing events that allow for an increase in diversity and the potential to select for a loss in avirulence to specific resistance genes within regions. The trend of suspected gene flow among neighboring fields is expected to be an ongoing issue with current agricultural practices.

scholarly journals Pathogenic Diversity of Phytophthora sojae in Ohio Soybean Fields

Plant Disease ◽  
2003 ◽  
Vol 87 (2) ◽  
pp. 139-146 ◽  
Author(s):  
A. E. Dorrance ◽  
S. A. McClure ◽  
A. deSilva
Keyword(s):  
Shannon Index ◽  
Phytophthora Sojae ◽  
Reduced Tillage ◽  
Management Tools ◽  
Tillage Practices ◽  
Soybean Cultivars ◽  
The Mean ◽  
Production Practices ◽  
Rps Gene ◽  
Pathogenic Diversity

Problems with early season soybean stand establishment, and an increase in incidence of Phytophthora root and stem rot caused by Phytophthora sojae, prompted a reassessment of the pathogen population in Ohio. Earlier studies had indicated a potential for pathogen adaptation to commonly deployed Rps genes in soybeans. Fifty-seven fields, part of an earlier study in 1990 and 1991, along with 29 additional fields were sampled in either 1997 or 1999. Two soybean cultivars, Sloan (rps) and Resnik (Rps1k), were used as bait in a seedling bioassay to isolate P. sojae from the soil samples. P. sojae was recovered from 82 of the 86 fields sampled. Of the 429 isolates recovered from these soils, 325 and 104 were baited with soybean cultivars Sloan and Resnik, respectively. The P. sojae population in Ohio increased in the number of pathotypes (races) as well as in complexity since the earlier surveys. There were 72 and 202 pathotypes identified on 8 and 13 Rps gene differentials, respectively, in the current study. When the data were compared by location, 96, 65, 73, 78, 51, and 52% of the locations had at least one isolate with virulences to Rps1a, Rps1b, Rps1c, Rps1k, Rps3a, and Rps6, respectively. The mean complexity, the number of susceptible interactions on 8 differentials, increased from 3.01 to 4.06 between 1991 and 1997/1999. In addition, the pathogenic diversity as measured by the Shannon index increased from 2.71 to 3.28 for isolates recovered from the 57 fields sampled in both surveys. Producers whose fields were sampled were surveyed to determine if changes in the P. sojae population could be linked with production practices. There was a significant association between (P ≤ 0.05) reduced tillage practices and the presence of isolates that had virulence to Rps1k; reduced tillage fields also had isolates with virulence to a greater number of differentials. Due to the percentage of isolates that have virulence to many of the Rps genes, it is questionable how long a single Rps gene or several stacked Rps genes will remain viable disease management tools for P. sojae, unless a novel Rps gene is identified.

Detached-petiole inoculation method to evaluate Phytophthora root rot resistance in soybean plants

2017 ◽  
Vol 68 (6) ◽  
pp. 555
Author(s):  
Yinping Li ◽  
Suli Sun ◽  
Chao Zhong ◽  
Zhendong Zhu
Keyword(s):  
Root Rot ◽  
Dominant Gene ◽  
Phytophthora Sojae ◽  
Single Dominant Gene ◽  
Phytophthora Root Rot ◽  
Inoculation Methods ◽  
Inoculation Technique ◽  
Soybean Cultivars ◽  
F2 Population ◽  
Soybean Resistance

Phytophthora root rot (PRR) caused by Phytophthora sojae, is one of the most destructive soybean diseases. The deployment of resistant cultivars is an important disease management strategy. To this aim, the development of a fast and effective method to evaluate soybean resistance to P. sojae is strategic. In this study, a detached-petiole inoculation technique was developed and its reliability was verified in soybean cultivars and segregant populations for PRR resistance. The detached-petiole and hypocotyl inoculation methods were used to assess the resistance of soybean cultivars, the F2 population of a Zhonghuang47 × Xiu94-11 cross, and the derived F2:3 population. The reactions of 13 analysed cultivars to three P. sojae isolates were consistent between the two inoculation techniques. The reactions of the F2 and F2:3 populations to isolate PsMC1 were 95.20% similar between the two inoculation methods. The segregation of the resistance and susceptibility fit a 3 : 1 ratio. Our results suggest that the detached-petiole technique is a reliable method, and reveal that the PRR resistance in Xiu94-11 is controlled by a single dominant gene. The phenotypic ratios of the tested Jikedou2 × Qichadou1 F2 population using the detached-petiole inoculation technique fit a 3 : 1 ratio (Resistance : Susceptibility). This demonstrated that Qichadou1 contains a single dominant gene conferring resistance to P. sojae. Our new detached-petiole inoculation technique is effective, reliable, non-destructive to the plant, and does not require an excessive amount of seeds. It may be suitable for the largescale screening of soybean resistance to multiple P. sojae isolates.

Evaluation of Soybean Cultivars with the Rps1k Gene for Partial Resistance or Field Tolerance to Phytophthora sojae

Crop Science ◽  
2006 ◽  
Vol 46 (6) ◽  
pp. 2427-2436 ◽  
Author(s):  
C. R. Ferro ◽  
C. B. Hill ◽  
M. R. Miles ◽  
G. L. Hartman
Keyword(s):  
Partial Resistance ◽  
Phytophthora Sojae ◽  
Soybean Cultivars

scholarly journals Pathotype Diversity of Phytophthora sojae in Eleven States in the United States

Plant Disease ◽  
2016 ◽  
Vol 100 (7) ◽  
pp. 1429-1437 ◽  
Author(s):  
A. E. Dorrance ◽  
J. Kurle ◽  
A. E. Robertson ◽  
C. A. Bradley ◽  
L. Giesler ◽  
...  
Keyword(s):  
United States ◽  
Partial Resistance ◽  
The United States ◽  
Phytophthora Sojae ◽  
Soil Samples ◽  
The State ◽  
Soybean Seedling ◽  
Northern Regions ◽  
Rps Gene

Pathotype diversity of Phytophthora sojae was assessed in 11 states in the United States during 2012 and 2013. Isolates of P. sojae were recovered from 202 fields, either from soil samples using a soybean seedling bioassay or by isolation from symptomatic plants. Each isolate was inoculated directly onto 12 soybean differentials; no Rps gene or Rps 1a, 1b, 1c, 1k, 3a, 3b, 3c, 4, 6, 7, or 8. There were 213 unique virulence pathotypes identified among the 873 isolates collected. None of the Rps genes were effective against all the isolates collected but Rps6 and Rps8 were effective against the majority of isolates collected in the northern regions of the sampled area. Virulence toward Rps1a, 1b, 1c, and 1k ranged from 36 to 100% of isolates collected in each state, while virulence to Rps6 and Rps8 was less than 36 and 10%, respectively. Depending on the state, the effectiveness of Rps3a ranged from totally effective to susceptible to more than 40% of the isolates. Pathotype complexity has increased in populations of P. sojae in the United States, emphasizing the increasing importance of stacked Rps genes in combination with high partial resistance as a means of limiting losses to P. sojae.

scholarly journals Soybean Root Suberin and Partial Resistance to Root Rot Caused by Phytophthora sojae

2008 ◽  
Vol 98 (11) ◽  
pp. 1179-1189 ◽  
Author(s):  
Kosala Ranathunge ◽  
Raymond H. Thomas ◽  
Xingxiao Fang ◽  
Carol A. Peterson ◽  
Mark Gijzen ◽  
...  
Keyword(s):  
Glycine Max ◽  
Root Rot ◽  
Partial Resistance ◽  
Infection Process ◽  
Phytophthora Sojae ◽  
Epidermal Cells ◽  
Chemical Defenses ◽  
Stem Rot ◽  
Subsequent Growth ◽  
Initial Infection

Phytophthora sojae is the causal agent of root and stem rot of soybean (Glycine max). Various cultivars with partial resistance to the pathogen have been developed to mitigate this damage. Herein, two contrasting genotypes, the cultivar Conrad (with strong partial resistance) and the line OX760-6 (with weak partial resistance), were compared regarding their amounts of preformed and induced suberin components, and to early events during the P. sojae infection process. To colonize the root, hyphae grew through the suberized middle lamellae between epidermal cells. This took 2 to 3 h longer in Conrad than in OX760-6, giving Conrad plants more time to establish their chemical defenses. Subsequent growth of hyphae through the endodermis was also delayed in Conrad. This cultivar had more preformed aliphatic suberin than the line OX760-6 and was induced to form more aliphatic suberin several days prior to that of OX760-6. However, the induced suberin was formed subsequent to the initial infection process. Eventually, the amount of induced suberin (measured 8 days postinoculation) was the same in both genotypes. Preformed root epidermal suberin provides a target for selection and development of new soybean cultivars with higher levels of expression of partial resistance to P. sojae.

scholarly journals Characterization of Components of Partial Resistance, Rps2, and Root Resistance to Phytophthora sojae in Soybean

2007 ◽  
Vol 97 (5) ◽  
pp. 655-662 ◽  
Author(s):  
Santiago Mideros ◽  
Mizuho Nita ◽  
Anne E. Dorrance
Keyword(s):  
Partial Resistance ◽  
Dominant Gene ◽  
The United States ◽  
Phytophthora Sojae ◽  
Lesion Length ◽  
Infection Frequency ◽  
Resistant Genotype ◽  
Soybean Genotypes ◽  
Incomplete Resistance ◽  
Root Resistance

Phytophthora root and stem rot of soybeans caused by Phytophthora sojae is a serious limitation to soybean production in the United States. Partial resistance to P. sojae in soybeans is effective against all the races of the pathogen and is a form of incomplete resistance in which the level of colonization of the root is reduced following inoculation. Other forms of incomplete resistance include the single dominant gene Rps2 and Ripley's root resistance, which are both race-specific. To differentiate partial resistance from the other types of incomplete resistance, the components lesion length, numbers of oospores, and infection frequency were measured in eight soybean genotypes inoculated with two P. sojae isolates. The Rps2 and root-resistant genotypes had significantly lower oospore production and infection frequency compared with the partially resistant genotype Conrad, while the root-resistant genotype also had significantly smaller lesion lengths. However, the high levels of partial resistance in Jack were indistinguishable from Rps2 in L76-1988, based on the evaluation of these components. Root resistance in Ripley and Rps2 in L76-1988 had similar responses for all components measured in this study. Partial resistance expressed in Conrad, Williams, Jack, and General was comprised of various components that interact for defense against P. sojae in the roots, and different levels of each component were found in each of the genotypes. However, forms of incomplete resistance expressed via single genes in Ripley and Rps2 in L76-1988, could not be distinguished from high levels of partial resistance based on lesion length, oospore production, and infection frequency.

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